Solve SHM of a Pendulum: Calculate Length with T=1.2s & g=9.8

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SUMMARY

The discussion centers on calculating the length of a uniform steel bar acting as a physical pendulum with a period of 1.2 seconds and gravitational acceleration of 9.8 m/s². The correct formula for a physical pendulum is L = (T²g)/(4π²), which was initially misapplied, leading to an incorrect length of 0.36 m. After clarification, the user successfully recalculated the length using the appropriate physical pendulum considerations, confirming the need to adjust the standard simple pendulum formula.

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Homework Statement


A uniform steel bar swings from a pivot at one end with a period of 1.2 seconds. How long is the bar?


Homework Equations


T=2[itex]\pi[/itex][itex]\sqrt{L/g}[/itex]


The Attempt at a Solution


I manipulated this equation to solve for L, giving me L=[itex]T^{2}g/4\pi^{2}[/itex]
Plugged in T=1.2 seconds and g=9.8. Answer I got was (to two significant figures) 0.36 m. But apparently that answer is wrong so I don't know what I am missing or if I am using the wrong equation.
 
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LunaTech said:
But apparently that answer is wrong so I don't know what I am missing or if I am using the wrong equation.
The equation you are using is for a simple pendulum, where all the mass is concentrated at the end. When the mass is spread out, as in your problem, you have what is called a physical pendulum, so you'll need to modify that formula a bit. Read this: Physical Pendulum
 
That clears things up a bit. I got the answer now. Thanks.
 

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